1. Technical Field
The present disclosure relates to devices, systems, and methods for controlling parking and/or emergency brakes in vehicles having an air brake system.
2. Description of Related Art
Conventional heavy-duty vehicle air brake systems use mechanical pneumatic push/pull valves to set and release a vehicle parking brake. An air parking brake system uses compressed air to apply the service brakes and parking brake. A brake pedal located on the floor of a vehicle cab is usually depressed to actuate the service brake, whereas a push/pull handle located on the vehicle dash is used to actuate the parking brake. The parking brake is generally a spring brake that is normally engaged, meaning air pressure must be applied to the parking brake chamber in order to release it. That is, when there is no air pressure present, the parking brake is applied. In contrast, air pressure is required to set service brakes (i.e., depressing the brake pedal actuates a control valve allowing air pressure to travel to the service brake). Therefore, if a vehicle loses air pressure, then it loses the ability to apply the service brakes. But, this also means the parking brake will automatically engage to slow the vehicle down. Similarly, when the vehicle is parked and/or not in use, the operator can engage the parking brake to prevent the vehicle from moving from the parked position.
Most large over the road vehicles, school buses, transit vehicles and others have air brakes. In many states, including Washington and Oregon, for example, there are regulations requiring school bus operators to set the parking brake each time a student is loaded (or unloaded), which means the brake must then be released to continue to the next stop. Actuating parking brakes on most buses (and other vehicles with air brakes) requires an extended reach and a high push/pull force to operate with each pickup and drop off (see Washington Department of Labor and Industries, memo August 2010). Consequently, setting and releasing a school bus parking brake using a push/pull valve repeatedly throughout a work shift can leave drivers with sore or seriously injured shoulders, elbows, and/or wrists.
One solution to this problem has been to use a mechanical lever that fits under the push/pull valve button, which allows drivers to place his/her fingers under the lever to mechanically set the brake. But, the lever does not provide any assistance in releasing the brake (see www.maxiebrakerelease.com). Other systems only set the parking brake by placing a dump valve, activated by the student load lights and the door switch, in the brake line between the air supply and the push/pull valve (see www.safetybrake.com), or only set the brake when the driver has left the driver's seat and opened the door (see U.S. Pat. No. 6,322,159).
From the foregoing, a need is apparent for alternative or improved push/pull valve devices, systems, and methods for controlling parking and/or emergency brakes in vehicles having an air brake system so that injury to operators of such vehicles is decreased, minimized or eliminated.